For the first time, researchers at the University of Tokyo have created an RNA molecule that duplicates, diversifies, and develops complexity in accordance with Darwinian evolution. This is the first empirical proof that basic biological molecules may give rise to sophisticated living systems.
There are many major questions in life, not the least of which is “Where did we come from?” Perhaps you’ve seen T-shirts with images ranging from ape to human (to tired office worker). But what about going from a basic molecule to a complicated cell to an ape? For decades, one theory has held that RNA molecules (essential for cell activities) existed on ancient Earth, presumably with proteins and other biological components. Then, some 4 billion years ago, they began to self-replicate and evolved from a single basic molecule to a vast array of complex compounds. This gradual evolution may have finally resulted in the creation of life as we know it, with its diverse variety of animals, plants, and everything in between.
Despite several talks on this hypothesis, it has been challenging to physically develop such RNA replication systems. However, in a study published in Nature Communications, Project Assistant Professor Ryo Mizuuchi and Professor Norikazu Ichihashi of the University of Tokyo’s Graduate School of Arts and Sciences, along with their team, describe how they carried out a long-term RNA replication experiment in which they witnessed the transition from a chemical system to biological complexity.
The crew was ecstatic by what they observed. “We discovered that the single RNA species developed into a sophisticated replication system: a replicator network composed of five kinds of RNAs with various relationships, suggesting the possibility of a long-envisioned evolutionary transition scenario,” Mizuuchi said.
In comparison to previous empirical studies, this new result is novel because the team used a unique RNA replication system that can undergo Darwinian evolution, i.e., a self-perpetuating process of continuous change based on mutations and natural selection, allowing different characteristics to emerge and those that were adapted to the environment to survive.
“To be honest, we were skeptical that such varied RNAs could develop and coexist,” Mizuuchi said. “The ‘competition exclusion principle’ in evolutionary biology holds that many species cannot live if they compete for the same resources. This implies that the molecules must devise a strategy for using various resources sequentially in order to maintain diversity. Because they are just molecules, we questioned whether nonliving chemical species might spontaneously create such innovation.”
So, what comes next? Mizuuchi claims that “When compared to organic creatures, the simplicity of our molecular replication mechanism enables us to analyze evolutionary events with remarkable detail. Our experiment’s observation of the emergence of complexity is just the beginning. Many more processes must occur in order for life systems to arise.”
Of course, there are many unanswered concerns, but this study has offered further scientifically based insight into a conceivable evolutionary path that an early RNA replicator may have followed on primeval Earth. “The discoveries might offer a hint to addressing the ultimate issue that humans have been asking for thousands of years — what are the beginnings of life,” Mizuuchi added.
